Ink tank structure

ABSTRACT

An ink tank for storing ink supplied to an ink jet recording head includes an ink tank body, an ink absorbing member inserted in the ink tank body in a compressed state, an atmosphere communicating port for communicating an inner space of the ink tank body with the atmosphere, and an ink supply port coupled to the ink jet recording head and serving as an ink supply port. A corner of the ink absorbing member which would be located near the atmosphere communicating port is cut out, a portion of the ink absorbing member around the cutout area is partly released in a degree of compression as compared with the other portion thereof under the state where the ink absorbing member is inserted in the ink tank body in a compressed state, and a space area is formed between the cutout area of the ink absorbing member and the atmosphere communicating port. The ink absorbing member is prevented from entering a buffer chamber, the ink impregnated in the ink absorbing member is uniformly supplied to the recording head, and the ink is prevented from leaking to the outside even if the cartridge is subjected to a thermal impact or a pressure reduced state.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ink jet cartridge for an ink jetrecording apparatus wherein image information is recorded by ejectingink or the like toward a recording medium.

2. Description of the Related Art

Heretofore, an ink jet recording apparatus wherein image information isrecorded by ejecting ink or the like toward a recording medium hasemployed an ink jet cartridge comprising a recording head for formingdroplets of the ink ejected toward the recording medium and an ink tankfor containing the ink and supplying the ink to the recording head, therecording head and the ink tank being joined together.

FIG. 1 is a cross-sectional view showing the structure of one prior artink jet cartridge.

As shown in FIG. 1, the prior art ink jet cartridge mainly comprises arecording head 27 from which ink is ejected toward a recording medium(not shown), and an ink tank 20 in which the ink to be ejected from therecording head 27 is stored. The ink tank 20 contains an ink absorbingmember 21 for retaining the ink that is impregnated therein. Also, theink tank 20 has an ink supply port 22 through which the ink retained bythe ink absorbing member 21 is supplied to the recording head 27, and anatmosphere communicating port 23 through which the atmosphere outsidethe ink tank 20 is communicated with the air inside the ink tank 20 toprevent a negative pressure in the tank inner space from risingexcessively. Further, as disclosed in Japanese Patent Laid-Open No.3-101971, the ink tank 20 is provided on its inner wall surfaces withribs 24 to 26 which serve to distribute the ambient air introducedthrough the atmosphere communicating port 23 to various portions of theink absorbing member 21, enabling the ink impregnated in the inkabsorbing member 21 to be evenly introduced to the ink supply port 22.In a portion of the rib 24 near the atmosphere communicating port 23,the height of the rib 24 projecting from the inner wall surface of theink tank 20 is greater than in the other portion of the rib 24 so thatthe ambient air introduced through the atmosphere communicating port 23is certainly supplied to the ink absorbing member 21.

In the ink jet cartridge described above, the ink impregnated in the inkabsorbing member 21 is supplied to the recording head 27 through the inksupply port 22 by the capillary-attraction depending on consumption ofthe ink in the recording head 27. The ink is then ejected toward therecording medium from the recording head 27. Corresponding to the amountof the ink consumed, the ambient air is introduced to the ink tank 20through the atmosphere communicating port 23.

In order to that the ink absorbing member 21 can properly retain the inktherein, the amount of the ink impregnated in the ink absorbing member21 must be less than the volume of the ink absorbing member 21, whileallowing the ink absorbing member 21 to develop the capillaryattraction. To this end, a vacant space (a portion A in FIG. 1) wherethe ink is not impregnated from the beginning necessarily exists in theink absorbing member 21. No matter where the vacant space exists, theink absorbing member 21 can sufficiently develop its function ofretaining the ink therein. But if the vacant space exists near the inksupply port 22, the ink flow may be blocked to prevent the ink frombeing supplied to the recording head 27. To avoid that the vacant spacewhere the ink is not impregnated will exist near the ink supply port 22,the ink is poured into the ink tank through the ink supply port 22 inthe manufacture process.

The ink poured through the ink supply port 22 flows through the inkabsorbing member 21 and reaches the rib 26. Then, the ink passes gaps orguide paths formed by the ribs 26, 25 and 24 and comes to the side nearthe atmosphere communicating port 23. The ink is thus impregnated in theink absorbing member 21 while finally leaving a vacant space in theportion A.

Here, the ink absorbing member 21 is inserted in the ink tank 20 in acompressed state.

In the prior art ink jet cartridge described above, however, because aportion of the rib 24 near the atmosphere communicating port 23 projectsfrom the inner wall surface of the ink tank with greater height than inthe other portion of the rib 24 so that the ambient air introducedthrough the atmosphere communicating port 23 is certainly supplied tothe ink absorbing member 21, a portion B of the ink absorbing member 21where it bumps the above higher portion of the rib 24 is brought into amore compressed state than in the other portion of the ink absorbingmember 21 when the ink absorbing member 21 is inserted in the ink tank20 in a compressed state. Therefore, when the ink is poured into the inktank 20, the ink is impregnated in a more amount in the portion B of theink absorbing member 21.

In practical use, there occur no problems even with the ink soimpregnated in the ink absorbing member. But if the ink jet cartridge issubjected to a thermal impact or a pressure reduced state while it isdelivered from the manufacture factory to the user, the air near theportion A expands, whereupon the ink accumulated in the portion B ispushed out to leak into a space where the atmosphere communicating port23 is located. In the worst case, the leaked ink is forced to exude tothe outside of the ink jet cartridge, resulting in a feat that theuser's hands or cloth may be stained with the ink leaked out when theuser opens the cartridge package.

Also, it is thought that the cartridge package is opened under anatmospheric pressure as low as 0.7 in some cases depending on thealtitude of the place where the user employs an ink jet cartridge. Undersuch a low atmospheric pressure, the ink may also leak to the outside ofthe ink jet cartridge as with the foregoing case.

To prevent the leakage of ink in those situations, a buffer chamber isgenerally provided between the atmosphere communicating port 23 and theink absorbing member 21, making it hard for the ink leaked out of theink absorbing member 21 to exude to the outside of the ink jetcartridge. However, the volume of the buffer chamber is so very smallthat the function of the buffer chamber is not always developedsatisfactorily.

Further, if the ink is impregnated in a portion of the ink absorbingmember 21 which enters the buffer chamber, the guide paths formed by theribs for distributing the ambient air introduced through the atmospherecommunicating port 23 to various portions of the ink absorbing memberare blocked off. This raises the problem that the ink impregnated in theink absorbing member is no longer uniformly supplied to the recordinghead 27.

SUMMARY OF THE INVENTION

The present invention has been accomplished in view of the above-statedproblems in the prior art, and its object is to provide an ink jetcartridge which can prevent an ink absorbing member from entering abuffer chamber and which can uniformly supply ink impregnated in the inkabsorbing member to a recording head.

Another object of the present invention is to provide an ink jetcartridge which can prevent ink from leaking to the outside even if thecartridge is subjected to a thermal impact or a pressure reduced state.

To achieve the above objects, the present invention provides an ink tankfor storing ink supplied to an ink jet recording head, the ink tankcomprising an ink tank body, an ink absorbing member inserted in the ink-tank body in a compressed state, an atmosphere communicating port forcommunicating an inner space of the ink tank body with the atmosphere,and an ink supply port coupled to the ink jet recording head and servingas an ink supply port, wherein a corner of the ink absorbing memberwhich would be located near the atmosphere communicating port is cutout, a portion of the ink absorbing member around the cutout area ispartly released in a degree of compression as compared with the otherportion thereof under the state where the ink absorbing member isinserted in the ink tank body in a compressed state, and a space area isformed between the cutout area of the ink absorbing member and theatmosphere communicating port.

With the present invention constituted as set forth above, a corner ofthe ink absorbing member which would be located adjacent to a bufferchamber when the ink absorbing member is inserted in the ink tank, iscut out so that any part of the ink absorbing member will not enter thebuffer chamber. Therefore, even if the ink absorbing member is pushedtoward the buffer chamber when it is inserted in the ink tank whilebeing compressed, the ink absorbing member can be surely prevented fromentering the buffer chamber. Additionally, guide paths formed forsupplying the ambient air introduced through the atmospherecommunicating port to the ink absorbing member will not be blocked off.

Also, the ink absorbing member is configured such that when it isinserted in the ink tank, a space of which volume is at least 0.5 timethe volume of a vacant space in the ink absorbing member where the inkis not impregnated, is left near the atmosphere communicating port.Therefore, even if the air contained in the ink absorbing member expandsdue to, e.g., a pressure reduction outside the ink tank and the ink isforced to leak out of the ink absorbing member corresponding theexpansion of the air, the leaked ink is accommodated in the above spaceformed when the ink absorbing member is inserted in the ink tank, andthe ink is surely prevented from leaking to the outside of the ink jetcartridge.

Further, a corner of the ink absorbing member is cut out so that the inkabsorbing member will not contact a rib on the tank inner wall surfaceover a predetermined length near the atmosphere communicating port.Therefore, when the ink absorbing member is inserted in the ink tank ina compressed state, a portion of the ink absorbing member near theatmosphere communicating port is not compressed and no ink will beaccumulated near the atmosphere communicating port.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing the structure of one prior artink jet cartridge.

FIG. 2 is a cross-sectional view showing one embodiment of an ink jetcartridge of the present invention.

FIG. 3 a perspective view of the ink jet cartridge shown in FIG. 2.

FIG. 4 is a perspective view showing one embodiment of a recordingapparatus on which the ink jet cartridge of the present invention ismounted.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the present invention will be describedhereinafter with reference to the drawings.

FIG. 2 is a cross-sectional view showing one embodiment of an ink jetcartridge of the present invention.

FIG. 3 is a perspective view of the ink jet cartridge shown in FIG. 2.

As shown in FIG. 2, the ink jet cartridge of this embodiment mainlycomprises a recording head 17 from which ink is ejected toward arecording medium (not shown), and an ink tank 10 in which the ink to beejected from the recording head 17 is stored. The ink tank 10 containsan ink absorbing member 11 for retaining the ink that is impregnatedtherein. Also, the ink tank 10 has an ink supply-port 12 through whichthe ink retained by the ink absorbing member 11 is supplied to therecording head 17, and an atmosphere communicating port 13 through whichthe atmosphere outside the ink tank 10 is communicated with the airinside the ink tank 10 to prevent a negative pressure in the tank innerspace from rising excessively. Further, the ink tank 10 is provided onits inner wall surfaces with ribs 14 to 16 which serve to distribute theambient air introduced through the atmosphere communicating port 13 intovarious portions of the ink absorbing member 11, enabling the inkimpregnated in the ink absorbing member 11 to be evenly introduced tothe ink supply port 12. In a portion of the rib 14 near the atmospherecommunicating port 13, the height of the rib 14 projecting from theinner wall surface of the ink tank 10 is greater than in the otherportion of the rib 14 so that the ambient air introduced through theatmosphere communicating port 13 is certainly supplied to the inkabsorbing member 11.

Further, a corner of the ink absorbing member 11 which would come intocontact with the above higher portion of the rib 14 when the inkabsorbing member 11 is inserted in the ink tank 10, is cut out so as toprevent any part of the ink absorbing member 11 from contacting theabove higher portion of the rib 14. As a result, when the ink absorbingmember 11 is inserted in the ink tank 10 in a compressed state, its partnear the above higher portion of the rib 14 is not compressed.

In this embodiment, the volume occupied by the ink absorbing member 11is 10.5 cc and the volume of the ink poured is 8.1 cc. Since the netvolume of the ink absorbing member 11 (i.e., the volume of a spongystructure making up the ink absorbing member) is reduced 1.2 cc in acompressed state, the volume of the vacant space in the ink absorbingmember 11 where the ink is not impregnated is 1.2 cc.

An experiment was carried out by placing the ink jet cartridge describedabove in a depressurization test box under 0.67 atm. As a result, it wasfound that no ink leaked to the outside of the ink jet cartridge. Thereason is believed in that since a portion B of the ink absorbing member11 is not compressed by the rib 14, almost no ink exists in the portionB and, therefore, even when the air in a portion A (vacant space) of theink absorbing member 11 expands due to, e.g., a pressure reductionoutside the cartridge, only the air is expelled to move out of the inkabsorbing member 11 and the atmosphere communicating port 13 while theink is kept impregnated in the ink absorbing member 11.

Further, if the inner space of the ink tank is not sufficientlydepressurized during a step of pouring the ink, the poured ink may beimpregnated in the portion B of the ink absorbing member 11 and may leakto the outside due to, e.g., a pressure reduction outside the cartridge.With the foregoing point in mind, an experiment was carried out byfabricating the ink jet cartridge of this embodiment under the conditionwhere a degree of depressurization in the ink tank was intentionallylowered in the manufacture process, and placing it in a depressurizationtest box under 0.67 atm. As a result, it was confirmed that no inkleaked to the outside in the ink jet cartridge of this embodiment.

In this embodiment, the volume of a portion C in the tank inner spacewhere the ink absorbing member 11 is not present is 0.6 cc that is 0.5time the volume of the vacant space in the ink absorbing member 11 wherethe ink is not impregnated, i.e., 1.2 cc. Stated otherwise, it isestimated that the volume of the vacant space in the ink absorbingmember 11 where the ink is not impregnated expands 1.5 times or less dueto, e.g., a pressure reduction outside the cartridge. Therefore, bysetting the volume of the portion C where the ink absorbing member 11 isnot present to be 0.5 or more time the volume of the vacant space in theink absorbing member 11 where the ink is not impregnated, the ink issurely prevented from leaking to the outside even if the air in the inkabsorbing member 11 expands due to, e.g., a pressure reduction outsidethe cartridge.

An ink jet cartridge to which this embodiment is applied has a structurecomprising three ink tanks 10 joined together, as shown in FIG. 3.Accordingly, each of the ink tanks is constructed as a relatively thinstructure. By applying the present invention to such a thin ink tank,however, it is possible to suppress the leakage of ink through theatmosphere communicating port satisfactorily from the standpoint ofpractical use.

A recording apparatus mounting the foregoing ink jet cartridge thereonwill be described below.

FIG. 4 is a perspective view showing one embodiment of a recordingapparatus on which the ink jet cartridge of the present invention ismounted.

The ink jet recording apparatus shown in FIG. 4 comprises at least apickup roller 309, a feed roller 306 and a pinch roller 307 for jointlyfeeding a recording medium P, an ink Jet cartridge 301 which is arecording means for recording image information on the recording mediumP, a carriage 302 on which the ink jet cartridge 301 is mounted, a guideshaft 305 and a guide rail 312 which are fixed at their opposite ends toa frame 304 and support the carriage 302 such that the carriage isslidable in a direction perpendicular to the feed direction of therecording medium P and in a direction parallel to the plane of therecording medium P, a carriage driving belt 311, a carriage drivingmotor 310 and a driving pulley 313 for jointly reciprocally moving thecarriage 302 in a linear, direction, a home position sensor 319 forcontrolling the stop position of the carriage 302, a pressure plate 308,and a base 314.

Outside the recording area, there are provided a wiper 318 and a cap 317for respectively cleaning and capping the ink jet cartridge 301, an LFgear 321 for. transmitting the power of a feed motor (not shown) to thefeed roller 306, the LF gear 321 being provided at one end of the feedroller 306, as well as a clutch gear 320 and a pump gear 322 fortransmitting the power from the LF gear 321 to the cap 317. In the abovearrangement, when the pickup roller 309 and the feed roller 306 arerotated, the recording medium P is drawn to advance to a position facingthe ink ejecting surface of the ink jet cartridge 301 in this condition,the carriage driving motor 310 is driven to rotate the carriage drivingbelt 311, causing the carriage 302 to reciprocally move in a lineardirection along the guide shaft 306 and the guide rail 312. At the sametime, ink is ejected in accordance with a recording signal from the inkjet cartridge 301 mounted on the carriage 302. As a result, the imageinformation to be obtained is recorded on the recording medium P.

Furthermore, a corner of the ink absorbing member 11 which would belocated adjacent to a buffer chamber 19 when the ink absorbing member 11is inserted in the ink tank 10, is cut out so that any part of the inkabsorbing member 11 will not enter the buffer chamber. Accordingly, evenif the ink absorbing member 11 is pushed toward the buffer chamber 19when it is inserted in the ink tank 10 while being compressed, the inkabsorbing member 11 is surely prevented from entering the buffer chamber19.

The above feature is particularly advantageous for the ink jet cartridgehaving a structure where the ink absorbing member 11 tends to be pushedtoward the buffer chamber 19 with stronger forces, as experienced, e.g.,when the ribs 15, 16 are provided on the inner wall surface of the inktank defined by a tank lid 18 as shown in FIG. 2.

For the ink jet cartridge thus constructed, the amount of the inkremaining in the ink absorbing member 11 was examined after repeatingthe printing operation until ink was no longer ejected from therecording head 17. As a result, it was confirmed that the amount of theremaining ink was less than that in a comparative ink jet cartridgewherein the ink absorbing member 11 partly entered the buffer chamber19.

The present invention constituted as described above can provideadvantages as follows.

The ink absorbing member is configured such that when it is inserted inthe ink tank, a space of which volume is at least 0.5 time the volume ofthe vacant space in the ink absorbing member where the ink is notimpregnated, is left near the atmosphere communicating port. Therefore,even if the ink jet cartridge is subjected to a thermal impact or apressure reduced state, the ink leaked out of the ink absorbing memberis accommodated in the above space formed when the ink absorbing memberis inserted in the ink tank, and the ink can be surely prevented fromleaking to the outside of the ink jet cartridge.

Also, a corner of the ink absorbing member is cut out so that the inkabsorbing member will not contact the rib on the tank inner wall surfaceover a predetermined length near the atmosphere communicating port.Therefore, when the ink absorbing member is inserted in the ink tank ina compressed state, a portion of the ink absorbing member near theatmosphere communicating port is not compressed and no ink will beaccumulated near the atmosphere communicating port. In addition, air canbe smoothly introduced to the inner space of the ink tank, a negativepressure can be stably maintained even upon the ink being consumedabruptly, and the printing quality can be improved. Moreover, since theink tends to be easily consumed from a portion far from the ink supplyport, it is possible to increase the availability of the ink retained inthe ink absorbing member.

Further, according to the present invention, a corner of the inkabsorbing member which would be located adjacent to the buffer chamberwhen the ink absorbing member is inserted in the ink tank, is cut out sothat any part of the ink absorbing member will not enter the bufferchamber. Therefore, even if the ink absorbing member is pushed towardthe buffer chamber when it is inserted in the ink tank while beingcompressed, the ink absorbing member can be surely prevented fromentering the buffer chamber. As a result, it is possible to avoid areduction in the volume of the buffer chamber and prevent the ink fromleaking to the outside of the ink tank even if the pressure ortemperature outside the ink tank is reduced or raised to a considerableextent.

Additionally, since the guide paths formed for supplying the ambient airintroduced through the atmosphere communicating port to the inkabsorbing member are not blocked off but kept open, the ink impregnatedin the ink absorbing member can be evenly supplied to the recording headand, therefore, the ink can be used efficiently.

What is claimed is:
 1. An ink tank for storing ink supplied to an inkjet recording head, said ink tank comprising: an ink tank body, an inkabsorbing member held in said ink tank body in a compressed state, anatmosphere communicating port for communicating an inner space of saidink tank body with ambient atmosphere, and an ink supply port coupleableto said ink jet recording head, wherein: an area of said ink absorbingmember which would be located near said atmosphere communicating port iscut out in a range of 2.5% to 6.0% with respect to volume of said inkabsorbing member, a first portion of said ink absorbing member aroundthe cutout area is partly released in a degree of compression ascompared with other portions thereof under a state where said inkabsorbing member is held in said ink tank body in a compressed state,and a space area is formed between the cutout area of said ink absorbingmember and said atmosphere communicating port.
 2. An ink tank accordingto claim 1, wherein said ink absorbing member has an air layer in saidfirst portion under a state where ink is filled in said ink absorbingmember, and said space area is formed to have a volume at least 0.5 ormore times the volume of said air layer.
 3. An ink tank according toclaim 1, wherein ink is filled in said ink tank.
 4. An ink tankaccording to claim 1, wherein said ink tank comprises three ink tanksjoined together so that at least three kinds of ink can be stored insaid ink tank.
 5. An ink tank according to claim 4, wherein said threekinds of ink are yellow, magenta and cyan in color, and black color iscreated by mixing said three kinds of ink with each other.
 6. An inktank according to claim 1, wherein said ink absorbing member is formedof urethane foam.
 7. An ink tank according to claim 1, wherein said inkabsorbing member is formed of melamine foam.
 8. An ink jet cartridgecomprising: an ink jet recording head; and an ink tank connected to saidink jet recording head for storing ink supplied to said ink jetrecording head, wherein said ink tank comprises: an ink tank body, anink absorbing member held in said ink tank body in a compressed state,an atmosphere communicating port for communicating an inner space ofsaid ink tank body with ambient atmosphere, and an ink supply portcoupleable to said ink jet recording head wherein: an area of said inkabsorbing member which would be located near said atmospherecommunicating port is cut out in a range of 2.5% to 6.0% with respect tovolume of said ink absorbing member, a first portion of said inkabsorbing member around the cutout area is partly released in a degreeof compression as compared with other portions thereof under a statewhere said ink absorbing member is held in said ink tank body in acompressed state, and a space area is formed between the cutout area ofsaid ink absorbing member and said atmosphere communicating port.
 9. Anink jet cartridge according to claim 8, wherein said cartridge isdetachably mounted on a carriage provided in an ink jet recordingapparatus.
 10. An ink tank according to claim 1, wherein said space areais a single joined space area comprising both the space area formed bypartly cutting out said ink absorbing member and a space inherentlyformed in said ink tank body.
 11. An ink jet cartridge comprising: arecording head which records by ejecting ink toward a recording medium;an ink tank body defining a space in which an ink absorbing member isplaced for retaining ink; an atmosphere communicating port forcommunicating air between said ink tank body and ambience; a bufferchamber defining a buffer space extending outwardly beyond a spaceoccupied by said ink absorbing member between said ink tank body andsaid atmosphere communicating port; and a rib which is provided in aninner wall of said ink tank body opposite to said buffer chamber andwhich biases the ink absorbing member toward said buffer chamber,wherein a part of said ink absorbing member located adjacent said bufferchamber is cut away, thereby to prevent a part of the ink absorbingmember adjacent to said buffer chamber from entering said buffer spacedespite biasing by said rib.
 12. A recording device comprising an inkjet cartridge according to claim 11, wherein said ink jet cartridgeeffects recording by ejecting ink toward a recording medium.
 13. An inkjet cartridge according to claim 11, wherein said rib defines a firstspace adjacent the inner wall of said ink tank body and opposite to saidbuffer space, and further comprising an ink supply port for inkcommunication between said recording head and said ink tank body, saidink supply port being disposed remote from said buffer space and fromsaid first space.
 14. An ink jet cartridge according to claim 13,further comprising a second rib on a wall between sais buffer space andsaid first space, said second rib defining a second space, said secondspace for air communication between said buffer space and said firstspace.